Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 252232
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
332 PM PDT Mon Sep 25 2017

.SYNOPSIS...
Breezy north winds next few days for increased fire danger through
Wednesday morning. Remaining warmer than normal through the end
of the week with lighter winds.

&&

.DISCUSSION...
Satellite imagery indicates generally clear skies as a strong
upper level ridge builds over interior NorCal. Current
temperatures are running 3 to 6 degrees warmer compared to 24
hours ago. The strengthening high pressure system will keep stable
conditions and above normal temperatures across the forecast
area. Temperatures will continue to trend upward each day as
ridging strengthens and shifts inland. Overall, daytime highs
could be up to 5 degrees above seasonal normals through the short
term period with Valley highs topping out in the low 90s by the
middle of this week.

A combination of dry northerly flow, low afternoon minimum
humidity, and poor overnight recovery will maintain Red Flag
Warning conditions through Wednesday morning. Winds are expected
to decrease by Wednesday afternoon as the upper ridge axis centers
over the west coast and surface gradients relax.

&&

.EXTENDED DISCUSSION (Friday THROUGH Monday)
An upper level trough is expected to displace the high pressure
system starting Friday. Current model runs trending toward a
deeper, faster moving trough that will sweep through the area
Friday and Saturday. Slight cooling expected with this trough as
valley temperatures may fall back into the 80s, though have not
yet brought temperatures as low as models suggesting due to the
uncertainty of the situation. Upper level ridging builds up again
Sunday allowing valley temperatures to rise back into the 90s.
Models diverge even more after Monday as the ECMWF and Canadian
models bring a shortwave trough through the area on Monday,
whereas the GFS shows the shortwave remaining well east. For now,
no precipitation is expected with these systems as it will remain
north of the area. Strong northerly winds will set in Sunday after
the trough passes as the ridging builds over the west coast once
again. HEC

&&

.AVIATION...
VFR conditions expected for Valley TAF sites for the
next 24 hours. Northerly gusts up to 20kts possible in the
Sacramento Valley today 18-02z. Easterly gusts up to 30kt possible
over the Sierra crest and foothills through Wednesday morning.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 AM PDT Wednesday for Carquinez Strait
and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba,
Northern Sutter, and Butte County Below 1000 Ft-Eastern
Mendocino NF-Eastern Portion of Shasta/Trinity NF-Lake County
Portion of Lake-Napa-Sonoma Unit-Northern Motherlode From 1000
to 3000 Ft. Includes portions of Nevada-Yuba-Placer-Amador and
ElDorado Units-Northern Sacramento Valley to Southern Tehama
County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to
3000 Ft. Includes portions of Shasta-Trinity and Butte Units-
Northern Sierra Including Lassen NP and Plumas and Lassen NF/S
West of the Sierra Crest (West of Evans Peak-Grizzly Peak-
Beckworth Peak)-Northern Sierra Including the Tahoe and ElDorado
NF/S West of the Sierra Crest-Southeast Edge Shasta-Trinity NF
and Western Portions of Tehama-Glenn Unit-Southern Motherlode
From 1000 to 3000 Ft. Includes portions of Calaveras-Tuolumne
Unit-Southern Sacramento Valley in Yolo-Sacramento Far Western
Placer, southern Sutter and Solano County Below 1000 Ft-
Stanislaus NF West of the Sierra Crest.

&&

$$



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